The availability of vitamin A (retinol) and the availability of discarded rod outer segment membrane in the retina were varied independently in order to determine which had the greater influence on the accumulation of lipofuscin (aging pigment) in the retinal pigment epithelium (RPE). Rats missing all rod outer segments due to heredity, and rats missing most of their rod outer segments due to light damage were compared to normal rats on diets either deficient or adequate in vitamin A. Within each diet group, the RPE of rats which lacked photoreceptor outer segments exhibited only slightly less lipofuscin was always markedly less in vitamin A-deficient retinas. Even in retinas with photoreceptors present, vitamin A deprivation resulted in greatly reduced amounts of lipofuscin. In conclusion, the presence of outer segment membranes has some influence on lipofuscin accumulation, but retinol makes a much greater contribution. Perhaps retinol, which is known to be highly concentrated in the RPE and to exhibit dynamic turnover in the retina is involved directly in lipofuscin formation.